The present invention relates to metallic-based materials that can be interposed between dissimilar materials and improve adhesion therebetween. The present invention is also related to a method for adhering two layers of materials using an intermediate layer containing at least one shape memory alloy that exhibits superelastic effects, as well as constructions including such materials.
Various materials have been proposed for achieving adhesion between dissimilar materials. One difficulty encountered in joining dissimilar materials is the differences between mechanical properties, such as elastic moduli and yield strengths of the respective materials. Dissimilar materials exhibiting modulus mismatches may produce shear stress parallel to material interfaces that can compromise adhesion effectiveness. Such shear stresses may result in crack propagation along the interface leading to the delamination. It has been found that such phenomena can occur even when a joint or laminate is under tensile loading.
Polymeric adhesives, commonly called glues, have been used to bond various surfaces together. These adhesives can be formulated to exhibit very large recoverable strain, strong chemical interaction with the bonding surfaces, and capability of storing large amounts of elastic energy before failure. Unfortunately, polymeric adhesive formulations typically exhibit very small elastic moduli and yield strength compared to materials such as metals, metals matrix composites, and ceramics to be bonded. Thus, when polymeric adhesives are employed to bond materials such as metals and ceramics, the large elastic modulus mismatch and the low yield strength of the polymeric glues at the interfaces presents significant opportunity for adhesion failure.